PCB4683 Exam 3 Study Guide Questions
And Answers
1. Why the traditional notion of the length of the giraffe's neck was
questioned and what the new evidence contributes to the study of
adaptation -
correct answer ✅Originally, the theory was that giraffes evolved
long necks to be able to eat the tallest leaves, thereby escaping
from competition with other herbivores.
Simmons and Scheepers challenged this notion and offered an
alternative explanation for the giraffe's long neck. They found that
giraffes most often ate leaves at shoulder height, not from the tops
of trees. They also found that males with the longest necks have
the harest skulls, and suggested that maybe long necks evolved
because of male competition for females? Female necks also
became longer as a byproduct of selection for longer male necks.
From this stemmed the Neck-as-a-Weapon Hypothesis.
There IS evidence for selection on longer necks for reaching high
leaves, and there IS evidence of selection on longer necks for male-
male competition.
2. Examples of valid experiments and observational studies that
have tested adaptive function of structures or behavior -
,PCB4683 Exam 3 Study Guide Questions
And Answers
correct answer ✅Study that focused on the function of wing
markings and waving in Zonosemata
Observational study testing behavioural thermoregulation in Desert
Iguanas
Observational study on Garter snakes and their night retreats
3. Utility and necessity of the comparative method in studies of
adaptation -
correct answer ✅The purpose of the comparative method is to
remove the effects of evolutionary history from an analysis. This is
also known as phylogenetically independent contracts. The
fundamental rationale is that if taxa share a close evolutionary
history, they do not represent independent data points.
4. Phenotypic plasticity as an adaptive trait -
correct answer ✅Phenotypic plasticity is a trait that can evolve,
and may or may not be adaptive. Some genotypes from some
populations are more plastic than others, demonstrating that there
is genetic variation in the degree of plasticity
, PCB4683 Exam 3 Study Guide Questions
And Answers
Example: The Daphnia magna water flea usually produces asexually.
It was hypothesized that when the presence of fish is detected,
negative phototaxis (= swimming away from light) is more adaptive
5. How tradeoffs and constraints limit adaptation -
correct answer ✅Many factors can limit adaptive evolution:
- Tradeoffs
- Functional constraints
- Lack of genetic variation
- Multi-level selection
6. Natural selection below the level of the individual -
correct answer ✅We most typically think of natural selection
working at the level of the individual, favoring those better at
leaving behind more individual descendants. Natural selection
operates at the level of individuals, not at the level of groups or
species. In some cases, selection can happen at a level below that
of the individuals. If this happens, the individual and its
component(s) may be in opposition. Think multi-level selection,
where there can be two or more levels of selection in one organism
And Answers
1. Why the traditional notion of the length of the giraffe's neck was
questioned and what the new evidence contributes to the study of
adaptation -
correct answer ✅Originally, the theory was that giraffes evolved
long necks to be able to eat the tallest leaves, thereby escaping
from competition with other herbivores.
Simmons and Scheepers challenged this notion and offered an
alternative explanation for the giraffe's long neck. They found that
giraffes most often ate leaves at shoulder height, not from the tops
of trees. They also found that males with the longest necks have
the harest skulls, and suggested that maybe long necks evolved
because of male competition for females? Female necks also
became longer as a byproduct of selection for longer male necks.
From this stemmed the Neck-as-a-Weapon Hypothesis.
There IS evidence for selection on longer necks for reaching high
leaves, and there IS evidence of selection on longer necks for male-
male competition.
2. Examples of valid experiments and observational studies that
have tested adaptive function of structures or behavior -
,PCB4683 Exam 3 Study Guide Questions
And Answers
correct answer ✅Study that focused on the function of wing
markings and waving in Zonosemata
Observational study testing behavioural thermoregulation in Desert
Iguanas
Observational study on Garter snakes and their night retreats
3. Utility and necessity of the comparative method in studies of
adaptation -
correct answer ✅The purpose of the comparative method is to
remove the effects of evolutionary history from an analysis. This is
also known as phylogenetically independent contracts. The
fundamental rationale is that if taxa share a close evolutionary
history, they do not represent independent data points.
4. Phenotypic plasticity as an adaptive trait -
correct answer ✅Phenotypic plasticity is a trait that can evolve,
and may or may not be adaptive. Some genotypes from some
populations are more plastic than others, demonstrating that there
is genetic variation in the degree of plasticity
, PCB4683 Exam 3 Study Guide Questions
And Answers
Example: The Daphnia magna water flea usually produces asexually.
It was hypothesized that when the presence of fish is detected,
negative phototaxis (= swimming away from light) is more adaptive
5. How tradeoffs and constraints limit adaptation -
correct answer ✅Many factors can limit adaptive evolution:
- Tradeoffs
- Functional constraints
- Lack of genetic variation
- Multi-level selection
6. Natural selection below the level of the individual -
correct answer ✅We most typically think of natural selection
working at the level of the individual, favoring those better at
leaving behind more individual descendants. Natural selection
operates at the level of individuals, not at the level of groups or
species. In some cases, selection can happen at a level below that
of the individuals. If this happens, the individual and its
component(s) may be in opposition. Think multi-level selection,
where there can be two or more levels of selection in one organism
